<!DOCTYPE html>
<html>
 <head>
  <title> new document </title>
  <meta charset="utf-8">
	<style>
		body{
			margin:0;
			text-align:center;
		}
		canvas{
			background:#aaa;
		}
	</style>
 </head>
 <body>
	<canvas id="canvas">您的浏览器不支持Canvas绘图</canvas>
	<script src="app_v1.js"></script>
 </body>
</html>
